From: Zachary Amsden <zach@vmware.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
Daniel Hecht <dhecht@vmware.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Bug in on_each_cpu?
Date: Thu, 01 Mar 2007 12:31:33 -0800 [thread overview]
Message-ID: <45E73825.30800@vmware.com> (raw)
In-Reply-To: <20070301072225.9f00c36c.akpm@linux-foundation.org>
Andrew Morton wrote:
> The handler for smp_call_function() is called with local interrupts
> disabled (from the IPI handler).
>
> So to provide a consistent call environment for that handler, on_each_cpu()
> will also disable local interrupts when making the direct call on this CPU.
>
> Similarly the !CONFIG_SMP version of on_each_cpu() disables local
> interrupts when running the caller's function.
>
Yes, that is sensible. Something akin to on_each_cpu(synchronize_tscs)
would certainly not like interrupts coming in. Similarly, acpi_nmi
disable and probably rcu barriers as well. The irq disable here can
very validly be used as a barrier, but trying to ensure preserved shared
state with irq handlers over the call is a bug.
If one had all the spare time in the world, a new "sense" of irq disable
that communicated this fact would be nice from a static or dynamic
checking perspective.
Zach
------
sutra I.1 - atha linushasaanam
next prev parent reply other threads:[~2007-03-01 20:31 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <45E6AC1A.8050608@vmware.com>
[not found] ` <20070301024524.c7c8ea1a.akpm@linux-foundation.org>
2007-03-01 11:34 ` Bug in on_each_cpu? Zachary Amsden
2007-03-01 11:41 ` Rusty Russell
2007-03-01 11:47 ` Zachary Amsden
2007-03-01 15:22 ` Andrew Morton
2007-03-01 20:31 ` Zachary Amsden [this message]
2007-03-02 4:46 ` Ernie Petrides
2007-03-01 15:28 ` Andrew Morton
2007-03-01 20:03 ` Zachary Amsden
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